1. Field of the Invention
The present invention relates generally to apparatus for mitigating damage and injuries from an explosion inside a confined space, such as an explosion inside an ammunition storage magazine, a missile test cell, a missile maintenance facility, a bomb disposal vessel, a command and control center, or like structures. More particularly, the present invention relates to a water-filled blanket which may be deployed inside a structure to mitigate the gas pressure loading generated by an explosion inside the structure confining the explosion.
2. Description of the Prior Art
Explosive devices, such as projectiles, bombs, and missiles stored in an ordnance facility, will occasionally detonate accidentally, resulting in an explosion which may cause substantial damage and injuries. If the mass, strength and architecture of the structure are sufficient to fully or partially confine the explosion, then the by-products of the explosion will cause the buildup of high temperature gases. These high temperature gases, when expanding in a space with restricted venting, cause the buildup of gas pressures inside the facility. The magnitude of the peak gas pressure depends primarily on the type and weight of the explosive relative to the interior volume of the facility. The duration and total impulse of the gas pressure depend primarily on the degree of venting available for these gases to escape from the facility. The degree of venting, in turn, depends on the total area of openings in the building envelope, the volume of space in the building for the hot gases to expand into, the mass and strength of the building envelope, and the magnitude and location of the maximum credible explosion (MCE) inside the facility. The degree of confinement and venting in most weapons facilities is sufficient to produce a significant gas pressure loading inside the facility. Such a loading could cause a significant increase in the extent of damage and injuries inside and outside the weapons facility.
Most ordnance facilities used for the production, maintenance, assembly and repair of weapons are conventional unhardened, above-ground buildings. These ordnance buildings must be located a large distance from nearby inhabited facilities in order to limit the risk of injuries and damage from hazardous debris produced by the maximum credible explosion (MCE) in the ordnance facility.
Generally, the minimum safe separation distance from an ordnance facility encumbers a large area of land. For example, the minimum safe separation distance to inhabited facilities from an ordnance facility is 1,250 feet for an MCE (Maximum Credible Event)xe2x89xa630,000 pounds NEW (Net Explosive Weight). Thus, an ordnance facility containing less than 30,000 pounds NEW, a typical situation, encumbers 112 acres of land which is the area of a circle with a 1,250 feet radius. The minimum safe separation distance and encumbered land area are, in turn, dictated by the maximum strike range of hazardous fragments and debris. At today""s real estate prices, especially near the waterfront, the value of encumbered land often exceeds the acquisition cost of the ordnance facility.
The minimum safe separation distance from building debris is also dictated, in part, by the gas impulse developed when the explosion is confined by the building envelope. This gas impulse contributes significantly to the launch velocity of building debris and the resulting maximum strike range of hazardous debris. Thus, any device or method that significantly reduces the magnitude of this gas impulse would significantly reduce the maximum strike range of hazardous debris and the corresponding encumbered land area needed for the safety of people and property.
The present invention overcomes some of the difficulties of the traditional strategies for mitigating the effects of an explosion in that it comprises a relatively simple, yet highly effective water-based apparatus which mitigates the gas pressure loading developed inside the structure confining the explosion.
One embodiment of the present invention is a water-blanket which rests on each pallet of ordnance to mitigate the gas pressure loading from an inadvertent explosion of the ordnance. Each water-blanket includes a pair of storage modules with each module comprising a plurality of storage compartments for storing a predetermined quantity of water. The storage modules are joined by a zipper which allows the modules to be separated for ease in transport. The quantity of water in the water-blanket depends upon the type and quantity of explosive on each pallet, the total number of pallets, and the structural and venting characteristics of the surrounding facility.